Various applications exist wherein closely-spaced slots are to be defined through a relatively thin wall in the manufacture of a particular product. One specific example of an application is a connector housing for mounting a plurality of connector elements used in integrated circuit testing. The electrical connector elements are, typically, generally planar in configuration and are mounted in substantially parallel slots for rotation about an axis generally perpendicular to planes defined by the elements. The rotation is effected as contacts of the integrated circuit engage the connector elements, and a "wiping" action is thereby effected so that, at the interface between a connector element and a contact of the integrated circuit, a good electrical transmission path is established.
The spacing of the connector elements is, of course, dictated by the spacing of the contacts on the integrated circuit to be tested. Very frequently, the spacing is quite close. It is necessary, therefore, to provide slots in the housing mounting the electrical connectors which are spaced at the appropriate distances in view of the contact spacing on the IC.
The housing for mounting the connector elements, as will be able to be seen then in view of the disclosure to this point, provides an array of alternating slots and ribs. Typically, in view of the close spacing of the contacts on the IC, the ribs are very narrow. They are often only on the order of a range between 0.005 to 0.035 inches in thickness. In many cases they are less than 0.025 inches thick.
The problems in manufacturing a housing as discussed hereinbefore are complicated by the manner in which the connector elements are mounted in the housing. U.S. Pat. No. 5,069,269, which issued to the present Applicant on Dec. 3, 1991, illustrates elongated tubular elements, which can be either elastomeric or rigid in nature, which are received in troughs formed in oppositely facing surfaces of the generally thin wall of the housing. The connector elements illustrated in that patent are, in turn, hooked to the tubular members to accomplish mounting. It will be seen then that it is frequently necessary to provide a trough or troughs which run across the array of slots in which the connector elements are disposed.
The prior art has sought to provide appropriate manufacturing processes for a housing for mounting the electrical connector elements. A first proposed solution has been to form the housing employing an injection molding process. This has been the standard method for producing a low cost housing component for test sockets for semiconductor devices. Injection molding does, however, have economic, technical, and leadtime drawbacks. Tooling and developing costs incident to the injection molding of a housing can run as high as $90,000 dollars. The specific costs, of course, depend upon a number of factors including the number of connector elements to be provided for mounting. From a technical perspective, however, injection molding almost becomes precluded in view of the minute dimensions typically involved. In view of the very thin width dimension of ribs between connector element mounting slots (typically less than 0.025 inches), the material used for molding and the pressures required to inject the material make it virtually impossible to provide an acceptable product using this method.
Such a housing requires close tolerances. In the case of injection molding, dimensional accuracy is sacrificed. The material injected has some measure of shrinkage associated with the injection molding process, and such shrinkage becomes clearly evident after the housing is cured.
The second manufacturing possibility is water-jet cutting. Such a method, however, typically, produces a poor slot cut along the full length of each slot. Problems are typically encountered with the initial penetration of the water-beam. The initial penetration typically causes an enlarged hole. Further, however, the housing material, in the case of water-jet cutting, chips and fractures.
Another proposed solution is tool machining. Such a possibility is, however, unacceptable for a number of reasons. A housing takes too long to manufacture, and the probability of tool bits breaking is high. Even when bits do not break, the ribs defining the slots in the housing can deform during the manufacturing process. Such deformation occurs because of tool pressure causing the ribs to deflect.
Another potential solution to the manufacture of such a product is laser machining. Laser machining of plastics has been performed in numerous applications for a number of years. Limited success has been achieved with respect to high-temperature engineering plastics.
One of the major drawbacks to laser cutting of any engineering plastic is that a char residue can remain on the surface of the material that has been machined. Such a residue is, on occasion, electrically conductive. This is particularly unacceptable in the case of the manufacture of an electrical connector housing.
Other questions have remained with regard to utilization of laser machining such components. Should the connector element slots be formed first and then troughs for receiving tubular mounting members formed thereafter? It has been found that, by doing so, the slots tend to have rolled edges and machine burrs which are almost impossible to remove.
It is to these dictates and problems of the prior art that the present invention is directed. It is an improved method for manufacturing a product such as an electrical connector housing for mounting a plurality of connector elements.